Plastic failure criteria

[bhollman]

I am new to running LS-DYNA, and I do the model building in Ansys Workbench. I'm confuesd on how to set the failure criteria on say a metal for which I defined a bilinear curve.

I have a model that according to product specification can yield during a drop of the product, but not separate (break apart).


If material failure occurs at 6% elongation, is my effective plastic strain .06, and is this the failure criteria I input into Ansys as the effective plastic strain limit?

Thanks in advance for your help.

 

[MaddogMcCree]

Material failure at 6% elongation probably comes from a tensile testing. Be careful there as this failure is due to the geometry of the tensile specimen and not a failure characteristic to the material itself.

I would propose you to go by MAT_ADD_EROSION (from 9.71 R5 on well documented). As this requires a big amount of testing, maybe you keep it simple for the beginning.

 

[inline6]

it is quite reasonable when using ductile isotropic materials to carry out a uniaxial tensile test to obtain true stress vs true strain bilinear curve. This data can be used in a FE model for the material properties. Provided the plastic strains from the analysis are below the true strain at failure of test specimen (how much below needs some judgement)then that would be considered acceptable.

 

[bhollman]

Thanks everyone for your help.

Bill

 

[rb1957]

if they've bee helpful to you, the polite thing is to give them LPSs